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Crashing stuff into asteroids may be our best shot at saving the Earth

One day, maybe without warning, a rogue asteroid could slam into our planet and wipe out a city, a state, or — in the most severe case — life as we know it. (Remember what happened to the dinosaurs?)

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While the risk of such an event is slim, the consequences could be catastrophic. For this reason, scientists around the world are wrangling their best ideas on how best to steer asteroids off-course to thwart a potential Armageddon.

earth asteroid meteorite collision collides shutterstock
An illustration of an asteroid colliding with Earth. Shutterstock

One of the most promising methods they have doesn't require nuclear weapons, drilling, or any other science fiction-like scheme. Instead, it involves literally crashing a speeding spacecraft into a dangerous space rock.

It's called the "kinetic impact" technique and, in a new study, planetary geoscientist Megan Bruck Syal and her team at Lawrence Livermore National Laboratory have taken a big step toward showing it just might work.

A looming yet distant threat

The biggest roadblock to figuring out how to deflect asteroids stems from the rocks' elusiveness, Syal told Tech Insider.

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In a perfect situation, we could shoot a probe to an Earth-bound rock, take samples, and scuttle it back to Earth to help design the perfect asteroid-deflecting mission. But we don't currently have the resources to do that.

Asteroids drift at extraordinarily far distances from Earth, so it's hard to study them and know how they'd react to our schemes to push them off-course.

To make matters even more complicated, no two asteroids are alike. Each one has a drastically different shape, size, strength, material makeup, rotation, speed, and weight than its neighbor. One rocky body could be a lumbering and loose pile of rubble and another a high-speed body as dense as granite.

"There's just so much uncertainty that will always be there," Syal said. "Even if you send a scout mission ahead of time."

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Vadim Sadovski/Shutterstock

A systematic approach

To sift through the fray, Syal's team ran an advanced computer simulation that incorporates what we do know about asteroids.

The team modelled a collision between a spherical aluminum spacecraft and asteroids of differing strengths, shapes, rotations, and internal material compositions. They published the results in the May issue of the journal Icarus.

Syal's team found that the most important factor in determining whether you could nudge an asteroid off-course is the rock's strength. Crashing a probe into an asteroid composed of soft and loose material, such as lunar soil, Syal said, would give the rock a much different push than smashing it into an asteroid made of strong rock.

Syal's team also found that you could push a relatively small asteroid — one measuring about the size of a football field and weighing about 1 million metric tons (about as much as 5,500 blue whales) — off course with a probe zooming somewhere between 11,000 to 45,000 mph. (The New Horizons probe that flew past Pluto is currently traveling at about 32,000 mph.)

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According to Syal, this was the first time anyone has performed a systematic study of how different asteroid properties would determine the outcome of the kinetic impact technique.

asteroids near earth
NASA

A rocky problem

Slamming a speeding probe into an asteroid may sound crazy, but it's one of the simplest and most mature approaches we currently have of deflecting asteroids.

That doesn't mean the technique is without limitations. For one, it would only work on small asteroids. For larger asteroids that are coming in fast, Syal said, the only viable option would be to use a nuclear device. Essentially, we'd set off a large explosion on one side of the asteroid that would (hopefully) propel it in a different direction.

"You get a lot more bang for your buck in terms of mass delivered to the asteroid," Syal said.

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We'd also have to know about them far in advance of impact — ideally with about a 10-year lead time, Syal said.

While our current telescopes are pretty good at finding and tracking large asteroids, sniffing out the smaller ones is much, much harder.

Further, characterizing a space rock's physical properties before it slams into Earth is important in determining the best deflection technique, but that might be impractical or even impossible.

"Hopefully future missions to asteroids will be able to touch the material and play with it and get more of a sense of the geotechnical parameters of the rock," Syal said. "But right now we don't really have a good handle on those numbers."

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When it comes to asteroid deflecting missions, it's not a one-size-fits-all approach. The more information we can gather about an asteroid before it becomes an imminent threat, the more we can tailor a given strategy to thwarting a catastrophe.

Syal and her team are currently looking at how an asteroid's shape and variations in its internal structure affect its potential to be nudged out of the way. And in the meantime, she says that there's promise that future missions will be able to characterize asteroids.

"Getting to an asteroid and doing work is really highly valuable," Syal said. "I hope that happens."

NASA
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